To control an operation of, for example, a walking assisting apparatus for aiding a human being in walking or to control traveling motions of a bipedal walking robot, it is necessary to sequentially determine floor reaction forces acting on leg bodies of the human being or the bipedal walking robot (to be more specific, the forces from a floor that act on grounding portions of the leg bodies). Determining the floor reaction forces makes it possible to acquire moments or the like acting on joints of the leg bodies of the bipedal walking body, and to decide target auxiliary forces of the walking assisting apparatus or desired drive torques or the like of joints of the bipedal walking robot on the basis of the determined moments or the like.
As a technique for determining the floor reaction forces, one disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2000-249570 has been known. According to this technique, a floor reaction force of each leg body is defined as a resultant value (linear combination) of a plurality of trigonometric functions having mutually different cycles of 1/n (n=1, 2, . . . ) of a walking cycle, because time-dependent change waveforms of floor reaction forces of each leg body periodically change during steady walking of a bipedal walking body. In this case, weighting factors of the trigonometric functions for combining the plurality of trigonometric functions use predetermined values preset for each bipedal walking body or values obtained by adjusting the preset predetermined values according to topography.
However, the foregoing technique is adapted to determine floor reaction forces of the leg bodies for one step or a plurality of steps of the bipedal walking body. For this reason, it is difficult to accurately determine floor reaction forces if the gait of the bipedal walking body sequentially changes. Furthermore, to enhance the accuracy of determined floor reaction forces, the weighting factors of the trigonometric functions must be set for each bipedal walking body or adjusted according to topology or the like. This makes it difficult to accurately determine floor reaction forces by minimizing influences of environments under which bipedal walking bodies move or individual differences among bipedal walking bodies.
There has been known, for example, a bipedal walking robot having force sensors, such as six-axis force sensors, attached to ankles and foot portions of each leg body to determine floor reaction forces on the basis of outputs of the force sensors. There has been known another technique whereby a bipedal walking body is walked on a force plate installed on a floor to determine floor reaction forces from the outputs of the force plate.
According to the technology using force sensors, however, in order to determine the floor reaction forces of human leg bodies, in particular, force sensors have to be attached to ankles and foot portions, so that the force sensors inconveniently interfere with walking in normal living environments. The technology using force plates allows floor reaction forces to be determined only in environments wherein the force plates are installed.
The present invention has been made with a view of the aforementioned background, and it is an object thereof to provide a method of estimating floor reactions that permits floor reaction forces to be accurately determined in real time by a relatively simple technique and that is ideally suited for determining floor reaction forces of human beings, in particular, as bipedal walking bodies.
It is a further object of the present invention to provide a method of estimating joint moments of a bipedal walking body that allows moments acting on joints, such knee joints, of leg bodies to be accurately determined in real time by using an estimated value of a floor reaction force thereof.